Burner control system



SePt- 23, 1941- B. E. sHAw 2,256,766

BURNER CONTROL SYSTEM Filed Sept. 18, 1940 2 Sheets-Sheet 1 QJ. Ji/e Was/Holz *Sept 23, 1941- B. E. SHAW 2,256,766

BURNER CONTROL SYSTEM FiledSept. 18, 1940 2 Sheets-Sheet2 Patented Sept. 23, 1941 BURNER lCONTROL SYSTEM Burton E. Shaw, Bristol, Ind., assignor to `Penn Electric Switch Co., Goshen, Ind., a corporation of Iowa Application September 18, 1940, Serial No. 357,278

17 Claims.

My present invention relates to a burner control system particularly adaptable for oil yburner installations wherein the burner motor and the ignition mechanism for the burner are electrically energized and controlled in response to a room thermostat or the like.

One object of the invention is to provide a control system 'wherein combustion failure from a hot position quickly shuts down the burner and recycling occurs after an elapsed period of time, the recycling operations being repeated indefinitely. l

Another object is to provide for shut-down instead of recycling upon combustion failing to occur, the system being thereupon placed back into operation only by a manual resetting operation.

Another object is to provide a burner system of the general character shown in my Patent No. 2,080,589, to which has been added an auxiliary heater and associated mechanism effective to shut off the burner in less time than it is ordinarily shut down as a result of operation of a safety switch, the auxiliary heater effecting a recycling of the burner upon shutoff thereof after a predetermined period of time during which conditions that caused operation of the auxiliary heater may have time to clear up and permit restarting of the burner in the normal manner.

More specifically, it is an object of my invention to provide a system of interconnected control devices operated by aV relay coil and an ignition trip coil vso as to effect the desired circuit connections, making it possible to energize a safety switch heater for shutting down the burner by operation of a safety switch when combustion fails to occur and on the other hand to operate an auxiliary heater for quick shutoff of the burner and subsequent recycling thereof when combustion failure occurs after combustion has once been established.

Although my burner system is susceptible of various embodiments, it is unnecessary to fully describe and illustrate more than one such embodiment in a diagrammatic manner in order to give a' full understanding of the invention and its operation. Accordingly, I have illustrated diagrammatically the various switches and wiring together with the control elements and the controlled elements comprising my system in a series of figures showing different positions and circuit connections of the parts. In said illustrations: f

Figure l is a diagrammatic View of my burner control system showing the variousv parts thereof in idle position;

Figure 2 is a similar View showing the parts in starting position kas a result of room thermostat closure, with a dotted position ofthe safety switch mechanism assumed after a time period if combustion does not occur;

-Figure 3 is a similar View showing the run ning positions of the parts, and v Figure 4 is a similar View showing the position which the parts assume as a'result of combustion failure after combustion establishment, 'with resultant positioning of the parts for a recycling operation.

On the accompanying drawings, a transformer T is illustrated having a primary coil l5 and a secondary coil 25. The primary coil l5 is connected across line wires I0 and I2, whereby the secondary coil 25 furnishes a low voltage current for the control circuits. i

The line wire l0 is connected with a wire I6 leading, to` a motor switch MS. The motor switch has a bridging contact I1 and is connected by a wire I8 to one side of the burner f motor M, the other side of which is connected by wires I9 and 20 to the line wire l2. The motor side of the motor switch MS is connected by a wire 2| to an ignition switch IS, the switch blade of which is indicated at 22. Wires 23 and 24 connect the ignition mechanism Igp of the burner with the switch 22 Vand the wire 20.

One circuit of the transformer secondary 25 includes a wire 26, a room thermostat RT, 'a Wire'l, a switch blade 28 of an auxiliary heater :switch AHS,` a Ywire 29, a switch blade 3B of a safety switch SS, a wire 3l, a relay coil RC, wires 32 and 33, a safety switch heater SSH, wires 34 and 35, a switch blade 35 of a combustion switch CS, and a wire 31. Another cir- -cuit of the transformer secondary 25 includes a wire 38, a switch blade 39 of a holding switch HS, and wires 4i! and 4l. transformer secondary 2E through the holding switch HS includes a wire 38.

The holding switch HS when closed also establishes afourth circuit including a` wire 42, a switch blade43 of an ignition trip coil switch ITCS, a wire 44, an ignition trip coil ITC, and a wire 45. A fifth circuit includes a wire 46, a switch blade 41 of a second auxiliary heater switch AHS', a wire 48, an auxiliary heater AH, and a wire 49.

The relay coil RC includes an armature 50 normally inthe lowered position of Figure 1, which when the relay coil RC is energizedfwill A third circuit of the effect trip-ping of a trip mechanism 521-52- V52a--53 by means of a thrust connection 54.

Closure of the relay coil RC also, through thrust connections 55 and 55, closes the motor switch MS and the holding switch HS respectively.

Where the thrust connections have just operated, arrow heads are f shown toindicate the direction of such operation. Y The trip mechanism above referred to consists of the thrust rod pivotally mounted relative to the thrust element 54 and operable torelease l a catch 52 from an abutment 52a. Thereupon l the lever 53 swings from the position of Figure 1 l to the position of Figure 2 to close the ignition i switch IS through a thrust element 51, open the thrust'connection 58 and close the ignition trip coil switch ITCS through a thrust element 59.

The ignition trip coil ITC when energized atl tracts an armature 60 which is normally in-lowered position. The armature 60, through thrust elements 515.52 land 63, respectively, closes the second auxiliary heater switch AHS', opens the lignition switch IS and opens the ignitiontrip coil switch ITCS.A At the same time, the Y'igni- `tiony trip coil ITC de-energizes itself by opening lof the ignition trip coil switchITCS and, re-

versely, through the thrust connections 58 and 58, resets the trip mechanism 5I,-52"-52a-53 from Vthe position of Figure 2 to the position of `Figure 3.

The safety switch heater SSH is adapted to `warp a. birnetal latch 64 toward the right for un-V `latching a lever 65 which thereupon through Aan operative connection 65 opens the safety switch Y SS to theposition shown by dotted lines in Figure 2. In order to reclose the safety switch, the lever 55 must be manually relatched Von the bimetal latch E4 as by pressing inwardly on a pin 'warp a bimetal bar B1 to the left, which thereupon through a thrust connection at 68 opens the auxiliary heater switch AHS. When the bar 61 cools down, the auxiliary heater switch AI-IS is reclosed.

PRACTICAL OPERATION 1. Idle position In the yopi-:ration of my burner control systern,'the parts are normally in the idle position of Figure 1. The transformer primary I5, it will be noted, is continuously energized so that a secondary'current is always available, but there are no secondary circuits when the system is in idle position. Y

2. Starting Ypos-tion Referring yto Figure 2, the room thermostat RTV has closed j-because o ,flowered room temperature, thusestablishing a starting circuit through Vthe following elements:k -RT-21-128--29- The armature 50 directly*` closes the motorv switch and the holding switch through the thrustI connections 55 and 55, whereby further circuits are established as follows: A motor circuit is established through elements IE-I `I-l -M-l. 9-

The auxiliary heater AH is adapted to` l Dash lines have been used to show diagrammat- .ically the thrust connections.

second auxiliary heater switch AHS through a w and 20. This is a line voltage circuit for operating the burner motor M. Control circuits `are established by the holding switch HS from the relay coil wire 32 as follows, under (a) and (b):

(a) A holding circuit through 33-39--40 and 4l, whereby the relay coil is retained energized by the lower half only of the secondary coil 25, since it takes less current tohold the relay closed than to close it. With such an arrangement, a single relay is operable to .cut in at as low as 80% of the full line voltage, and to out out at a lpoint not lower than approximately of the Hfull line voltage.

(Z7) A safety switch heater circuit through 5l-Ll0-3S-38-33-SSH-34-35-35 and 31. The safety switch heater circuit is accordingly energized independently of the relay coil RC since the safety switch heater receives its current `from the upper half only of the transformer secondary 25.

The attraction of the armature 5t by the relay coil. RC also actuates 'the trip mechanism 5!- 52-52a-53 to the position of Figure 2 by the thrust element 5d' `pushing upwardly on thev thrust rod 5l, thereby lifting the catch 52 from,

the abutment 52a `and permitting the lever 53 to swing l'thecatch to the right past the abutment, which also'results in the offset of the catch dropping overthe edge of the rod 5L Movement of the lever V.5?, toward Athe right vresults in (a), closure of the ignition switch IS through the thrust connection 57; (b) opening of the second auxil-v iary heater switch AHS 'through the thrust connection 58, and (c), closure of the ignition'trip coil switch ITCS through the thrust connection 59. Thusthe ignition mechanism Ign is energized through elements 2l-22-23-Ign and 24Y from the` motor switch MS in one side to the line wire l2 through wire v2) on the other side. Opening of the switch AHS' eliminates the auxiliaryV heater AH from the circuit, whereas closure of the switch ITCS partially completes a circuit for the ignition trip coil ITC which is subsequently fully completed-through the combustion switch CS'as will hereinafter be described.

ZafShut-down position if combustion does not occur Further referring to Figure 2 if combustion does not occur the combustion switch CS will not move from its positionV illustrated, so that after a v time period, for instance forty seconds, the safety switch heater SSI-I will have radiated `enough heat to the bimetal element 64 to cause it to warp toward the right, thereby unlatching the lever 55 and permitting it through the thrust connection 55 to open the safety switch SS. Opening of the safety switch cuts off the current to the relay coil so that the motor switch and the holding switch are opened and the thrust rod 5! is retracted Ato the dotted position. The

system is now shut downuntil such time as a service man determines the cause of the trouble and rese-ts 4the safety switch mechanism by pressing the resetting pin 65a.

v v Y 3. Running/'position If combustion does occur, the switch blade 36 of the combustion switch CS will be moved from circuit relation witnthe wire35 tocircuit relati-on with the wire 45. Such movement is effected through a slip friction or notched disc slipping connection between a temperature rel sponsive element, such as a helical bimetal elev ment "69 responsive to temperature in the stack and the switch blade 36. By wayof example, one end of the element 69 is illustrated as attached to a stationary support and the other end attached to a rod 1I rotatable in the support-10.

The rod carries a notched disc' l2, the peripheryure 3 to the position of Figure 2, and thereafter" the disc 12 will slip past the blade 3B, keeping the blade in circuit relation to the wire35.

Closure of the combustion switch CS to the hot position of Figure 3 causes energization of the ignition trip coil ITC through elements lll'-` 42--43-44-ITC--45-36 and 31 Y(the switch blade 43 of the switch ITCS being still in the position of Figure 2, or the dotted position of Figure 3) Movement of the switch blade 36 of the combustion switch CS from circuit relation to the wire 35 de-energizes the safety switch heater SSH so that there will be no shut-down, as in the case of combustion failing to occur, as described under subheading 2a. Energization of the ignition trip coil ITC primarily opens the ignition switch IS through the thrust connection 62. Two secondary functions are performed by the ignition trip coil, consisting of (a) closure of the switch AHS through the thrustconnection El, and (b) opening of the ignition trip coil switch ITCS through the thrust connection 63, soA thatl current will not continue to ow through the ignition trip coil ITC. The mechanical relation of the parts is such that when theY armature 60 is attracted by the coil ITC, it will have sufficient momentum to open the ignition trip coil switch ITCS and relatch the trip mechanism 5|-52-52a-53 reversely through the thrust connections 58 and 59, in addition to opening the ignition switch IS and closing the auxiliary heater switch AHS and even though the coil ITC is de-energized by the switch ITCS.

4. Combustion failure after combustion esteblishment Figure 4 shows the position ofthe parts assurned as a result of combustion failing after it has once been established. First of all the combustion switch blade 36 will return from the position of Figure 3 to the position of Figure 4 due to a falling stack temperature. This establishes a circuit for the auxiliary heater 'AH through the following elements: lll'I--llll---Sn 46--41-48-AH-49-35-36 and 3l. The upper half of the transformer secondary 25 is therefore the source of current for the auxiliary heater AH.

The heater AH has less resistance than the safety'switch heater SSH, so that it can cause a shut-down relatively soon after combustion failure. For instance, it may be of suflicient heat radiating power to warp the bimetal element El to the position of Figure 4 within a space of some twenty seconds. Thus the time it takes for the combustion switch to return from the position of Figure 3 to the position of Figure 4 plus these twenty seconds isthe shutoff-time for the burner as a result olfc'o'mbustiongfailure after combustion establishment.

Warping of thebimetal velement 61 to the full line position-ofv Figurefl causes opening of the auxiliary' heater switch AHS directly through thethrust connection '68. The" elements AH- lland AHS are of recycling type, whereby cooling of the element'l'back to the position of Figure 3 will result in retraction ofthe thrust connection 63 and reclosure'of the auxiliary heater switch blade 28. Closure of the blade 28 ria-establishes the.' startingcircuitY (and the running circuit, if combustion occurs), but if it again fails after establishment the recycling or purging period is repeated. If, however, combustion fails to be establishedafter being established and then failing, the shut-down under subheading 2a. will occur.

The purging period `is preferably of two or three minutes duration and the major portion of this period is determined by the time it takes the bimetal element 61 to cool from the position of Figure 4 to the position of Figure 3. The relatively fast heating auxiliary heater radiates so much heat tothe bimetal element 61 that it takes some two minutes or so for it to cool down, thereby giving a purging period of two minutes plus twenty seconds, plus whatever time it takes for the combustion switch 36 to move from hot to its opposite position. In Figure 4, the relay coil RC has been'de-ener'gized by lopening of its holding circuit through 38-39-40 and 4I, and accordingly the holding switchand motor switch are open for the purging-period; the dotted positions of Il and 39 being the positions of these parts before theswitch AHS opens.

I have shown my system in connection with intermittent ignition, whereas for continuous ignition the wires 2l and 23can be connected together and the ignition switch IS, together with thrust connections 51 and`62, can be eliminated. In such event the trip' coilITC would lthen serve as an actuator for only the switchesAHS and ITCS. I

From the foregoing disclosure, it is obvious that I have provided a system wherein positive shutdown is providedfor failure of combustion to occur. For the more frequently occurring failure of combustion after it has once been established, I provide a recycling orpurging operation which permits the burner` to recyclean infinite number of times, providing combustion failure occurs after the combustionhas been established to a sufficient degree to move the stack switch from closed cold position to closed hot position and thenA back to closed cold position. Thus I have both the positive shut-down feature for certain conditions, and the recycling feature for certain other conditions, which other conditions occur more frequently than initial failureof combustion to take place'. The arrangement is such that a purging period is started inless time through operation of the auxiliary heater AH than a shutdown operation through the safetyswit'ch heater SSI-I, which is a further desirable feature of the purging or recycling operation.

The characteristic ofy the auxiliary heater switch AHS and its associated mechanism 6l and AH whereby the element 6l Aheats up quickly to open the auxiliary heaterswitch'AHS and then cools down slowly to provide the purging period, is particularly the feature. which gives the desirable quick shut-down uponlflame failure after combustion, together with a lsufficient purging period toY .clearj away accumulated bases` so that restartingjcan be accomplishedfwtih safety. Also, v

i In accordance with the provisions of the patent i statutes, I have described my system together withtits principlel of operation, and have illustrated'the varioussteps of suchY operation. The

form' of system shown Vis one which I consider to being reclosed after a purging period determined by the time required for said rstauxiliary heater switch to cool back to normal position.

3 represent thebeSt-embodiment thereof, but I desire to have it understood that thedisclosure l is illustrative only and` that the invention may be carried out by other means within the scope of 3 the appended claims.'

. What I claim asn-ewV and desire to secure vby t Letters Patent of the United states is:

1V. In a burner system, a transformer, an initial room thermostat circuit including a room thermostat, 'an'auxiliary heater switch, means operableupon energization by the secondary fof said transformer to initiate Voperation of the burner, a safety switch heater V`and combustion switch i contacts; said combustion switch contacts being closed in the absence and open in the presence Vof i combustion, a second set of combustion switch :contacts open in the absence and closed in the i presence of combustion, a safety-switch normally 1 closed but opened by said safety switch heater 1 upon energization thereof fora predetermined i period of' time, a second circuit'energized by a portion only of said secondary of said trans-' former and including said room thermostat, said auxiliary heater switch, and said means, a holding switch for establishing said second circuit and 1 I for maintaining it when said first combustion switch contacts are separated, said holding switch n 'being' closed by energization of said means, a 1 third circuit energized by the remaining portion of said secondary and including said holding Q switch, said safety switch heater and vsaid first lcombustion switch contacts, said second andV Y thirdcircuits being establishedvand said-initial room thermostat being altered as to currentsupplied thereto by closure of said holding contacts,

I said first` combustion switch contacts failing to l open in the event that combustionY fails tooccur andjthereby maintaining said third circuit enf ergized until said safety switch heater opens said safety switch, a fourth circuit energized by said remaining portion of said secondary'and including said second combustion switch contacts, anv ignition trip coil and an ignition trip coil switch, an ignition switch for the burner closed by said means when energized and opened by said ignition trip coil when it is energized, said ignition z trip coil switch being also opened by said ignition trip coil to de-energize the trip coil ysubsequent 3 to opening` of the ignition switch thereby, and a fifth circuit through said holding switch energized by said remaining portion of said secondary and including Y an auxiliaryrheater and a second auxil- 1iary heater switch, said second auxiliary-heater switch being Vclosed by energization of said ignition trip coil andopened by energization of said `relay coil, said auxiliary heater being operable `upon energization to open said rst auxiliary heater switch in a period of time shorter than the period of time requiredV to opensaid safety switch upon energization of said safety yswitch lheater, said auxiliary heater being/energized by lclosure of said first combustion switchV contacts `as a result of combustion failure after combus- `tion establishmentfsaid auxiliary heaterswitch 2. In a burner system, a transformer, an initial room thermostat circuit including -a room thermostat, anv auxiliary heater switch, a relay operable upon energization by the secondary of said transformer to initiate operation of the burner, a safety switch heater andv combustion switch contacts, said combustion'switch contacts being closed in;Y the absence Yand open in the presence of combustion, ,a second set of combustionswitch contacts open `in the absence and closed in the presence of combustion, a safety switch normally closed but opened by said safety switchheater upon energization thereof for a predetermined i Yperiod of time, va second circuit energized by a portion only Qf saidV secondary of said transformer and including said room thermostat,said auxiliary heater'switch,. and said means, a holding switch for establishing said second circuit andfor maintaining it whensaid first combustion switch contactsare separated, .said holding switch being closed by energization of said relay, a third circuit energized by the remaining portion Yof said' secondary and including said holding switch, said safety switch heater andy said first combustion switch contacts, said second and third circuits being established and said initial room thermostat being altered as to current supplied thereto by closure of said holding contacts, said first combustion switchncontac'ts failing to open in theevent that combustion fails `to occur and therebyV maintaining Said third circuit energized until said safety switch heater opens said safety switch,

a fourth circuit energized by lsaid remaining portion of said secondary and including said second combustionswitch contacts and a trip coil, and a fifth circuit through -said holding switch energized' by said remaining portion of said secondary and including an auxiliary heater and a second auxiliary heaterswi'tch, said second auxiliary heater` switch being `closed by energization of said trip` coil and opened by 'energization of said relay coil,

said auxiliary heater being energized by closure means operable upon energization from said Vsource of current supply to initiate operation of ther burner, a safety switch heater and combustion switch contacts, said combustion switch contacts being closed in the absence'and open iii the presence of combustion, a second set of combustion switch contacts open in the absence' and closed in the ypresence of combustion, a

f safety switch normally closed but opened by said safety switch heater upon energization thereof for a predetermined period of time, a second circuit including said room thermostat, said auxiliary heater switch, and said means, a holding switch for establishing said second circuit and for maintaining it when said first combustionv tactsfailing to open in the event that combustion 'fails to occur and thereby maintaining said third circuit energized Auntil said safety switch heater opens said safety switch, a fourth'circuit including said second combustion switch contacts and an ignition trip coil, an ignition switch for the iary heater switch in a period of time shorterk than the period of time required to open said safety switch upon energization of said safety switch heater,l said auxiliary heater being energized by closure of said rst combustion switch contacts as a result of combustion failure after,

combustion establishment, said auxiliary heater switch being reclosed after a purging period determined by the time required for said first aux- Y iliary heater switch to cool back to normal position.

4. In a burner system, a transformer, an initial room thermostat circuit including a room thermostat, an auxiliary heater switch,.means operable upon energization by the secondary of said transformer to initiate operation of the burner, a first set of combustionswitch contacts "closed in the absence and open in the presence of combustion, a second set of combustion switch contacts open in the absence and closed in the presence of combustion, a second circuit energized by a portion only of'said secondary of said transformer and including said room thermostat, said auxiliary heater switch, and said means, a holding switch for establishing said second circuit and for maintaining it when said first combustion switch contacts are separated, said holding switch being closed by energization of said means, a third circuit energized by the remaining portion of said secondary and including said holding switch, and said first combustion switch contacts, said second and third circuits being established and said initial room thermostat being altered as to current supplied thereto'by closure of said holding contacts, a fourth circuit energized by said remaining portion of said secondary and including said second combustion switch contacts and a trip coil, and a fth circuitthrough ,said holding switch energized by said remaining portion of said secondary and including an auxiliary heater and a secondary auxiliary heater switch, said second auxiliary heaterl switchbeing closed by energization of said trip coil and opened by energization of said relay coi 1, saidrauxiliary heater being operable upon energization to open said first auxiliary heater switch in-a periodof time corresponding to movement of lsaid combustion switch from hot to cold position and said first auxiliary heater switch from cold to hot position, said auxiliary heaterbeing4 energized by closure of said first combustion switch contacts as a result of combustion failure after combustion establishment, said auxiliary heater switch being reclosed after a purging period determined by the time required for said first auxiliary iheater switch to move from hot to cold position'.v

5. In a burner system, a transformer, an initial room thermostat circuit including a` room thermostat, a heater element, means operable upon energization by the secondary of said trans- ,former to initiate operation of the burner, a

safety switch actuator and combustion switch contacts, said combustion switch contacts being closed in the absence and open in the presence of combustion, a second set of combustion switch contacts open in the absence and closed in the presence of combustion, a safety switch normally closed but opened by said safety switch actuator upon energization thereof for a predetermined `period of time, a second circuit energized bya portion only of said secondary of said transformer and including said room thermostat, said heater element switch, and said means, a hold- .ing switch for establishing said second circuit and for maintaining it when said first combustion A switch contacts are separated, said holding switch being closed by energization of said means, a third circuit energized by the remaining portion of said secondary and including said holding switch, said safety switch actuator and said first combustion switch contacts, said second and third circuits being established and said initial room thermostat being altered as to current supplied thereto by closure of said holding contacts, said first combustion switch contacts failingto open in the event that combustion fails to occur and thereby maintaining said third circuit energized g until said safety switch actuator opens said safety switch, a fourth circuit energized by said remaining portion of said secondary and including said second combustion switch contacts and a tripcoil, and a fifth circuit through said holding switch energized by said remaining portion of said secondary and including a heater element and a second heater element switch, said second heater element switch being clos-ed by energization of said trip coil and opened by energization of said relay coil, said heater element being energized by .closure of said first combustion switch contacts as a result of combustion failure after combustion establishment, said first heater element switch being reclosed after a purging period determined by the time required for said rst auxiliary element switch to cool back to normal position.

6. In a burner system, a transformer, an initial room thermostat circuit including a room thermostat, a circuit opener, a relay operable upon energization by the secondary of said transformer to initiate operation of the burner, a safety yswitch actuator and combustion switch contacts, said combustion switch contacts being closed in the absence and open in the'presence of combustion, a second set of combustion switch contacts open in the absence and closed in the presence of combustion, a safety switch normally closed but opened by said safety switch actuator upon energization thereof for a predetermined period of time, a second 'circuit energized by a portion only of said secondary of said transformer and including said room thermostat, said circuit opener, and said means, a holding switch for establishing said second circuit and for maintaining it when said first combustion switch contacts areA separated, said holding switch being 'closed by energization of said relay, a thirdV cirl cuit energized by the remaining portion of said secondaryV and including said holding switch, said safety switch actuator and said first combustion switch contacts, said first combustion 4 switch contacts failing to open in the event that combustion fails to occur and thereby maintaining said third circuit energized until said ysafety switch actuator opens said safety switch, a fourth 'circuit energized by said remaining portion of said secondary and includingsaid second combustion switch contacts and a trip coil, and

` nQrmal; position.

aryand including a thermally operable actuator Y `for said circuit opener and va second circuit opener, said jsecond circuit opener-being closed by -energi'zation-ofzsaid trip coil and opened by energization of V said relay-rcoil, said thermally x operable actuator being energized by closure of -Vsaidrst combustion switchconta'cts as a result 'ofcombustion failure after combustion -establishment, said first circuit opener being reclosed 'after a purgingperioddetermined vby the-time required for said thermally operable actuator for 'saidrst circuit opener to return to cold po ition.

7. An electric control system for oil burners andthe like-including an initial room thermostat circuit through a room thermostat, an auxiliary Y,heater switch, a relayV operable upon energization toV initiate' operation of the burneli'a safety switchheater and `closed cold' 'combustion switch contacts, av safety switch'normally closed-but opened by rsaid safetyy switch'heater upon energization thereof forV a predeterrnined'period'of thne, aV second circuit including said` room ther-s mostat, said auxiliary'heater switch; said safety switch andsaid relay,-a hoidin'gfswitch fores-V tablishing saidA second circuit and rfor maintain- Ving it `when said combustion Vswitch contacts are separated, said holding switchbeingclosed by energizationv of said means, a'l third circuit including said holding switch, said safety Yswitch 'heaterfand' said combustion switch contacts, said combustion switch contactsv uponopeningj due to combustion establishment Vdiscontinuingr said i third circuit and upon fail-urel to` Voper-1 `due to failure of combustion to occur causing said -third circuit to continue to be energized and thereby said safety switch heater` to ,openl said; safety switch, a fourthcircuit including a second set ofcombustion switch contacts whichclose hot 'and means to close a second auxiliary heater switch, 'and a fifth circuit through saidrholding switchY and. including said auxiliaryheater and a second auxiliary heater switch, said secondv auxiliary heater switch being closed by energizajtior1v of said means 'and opened by energzation of said relay, said auxiliary. heater Ybeing roperable uponk energi'zation to open said'auxiliary heater switch 'in a period of time shorter f than; the periodi of.' time required. to. open said safety switch. upon energization of-jjsaid safety 4switch heater, said auxiliary heater "being energizedA by yclosure, of' Said rst combustion switch contacts asaresult of combustion; failure after ccrnbustion has once been established, said auxilijary' heater switch being reclosed' after-a purging period determined by the time required for said auxiliary heater switch toy C001; lback 't0 8,. In a control system-for cil' burners and the like,V a, transf,orrner,` an initialV room thermostat Y'circuit including, ajroom thermostat; an auxiliary 'heater switch,Y means operable upon energizatifonby the secondary of' said' transformer to initiateoperationA of the burner, closedicold'combustionA switch contacts, a secondl circuit ener-V gizedby a portion only of said. secondary of' said transformer andv including said' room thermostat, said vauxiliary heater switchand. said' means, f ai.l holding swtchior establishing saidsecchd' circ cuitand for maintaining it when said combustion l jfswitchw contacts.l are separated; saidj holding -'SiftilllV beine.V Closed by. 'enersizatio'nf of, Vsaid ',means, athird circuitl 'energized by the remaint a can circuit through said holding switcn ener- 'gizedf by said remaining portion ofsaidv seconding portion of said secondary and including said holdin-gswitch and said combustion switch ccntacts, -saidcombustion switch contacts upon opening due to combustion establishment disconauxiliary heater switch being closed by energ-ization of said last means and opened by energizationofsa-id rst means, said auxiliary heater being energized/by closure of said rst combustion switch contacts as a result' of combustion failure after combustion has once beenestablished, -sa-id auxiliary heater switch being reclosed after a purging period determi-ned by the time required for said auxiliary heater switch to return to normal position.

9, In an electric control system for cil burners,

an initial room thermostat circuit including a room thermos-tat', aw heaterswitch, means operable-upon energization to initiate operation of the burner; closed coldcombustion switch contacts including saidroom thermostat, said heater switch and saidmeans, a holding switch for establ-i'shingsaid second circuit and formaintain- -ingitestablished whensaid combustion switch contacts aresepa-rated, said holding switchbeingclosed by-energ-ization o-fsaid means, a third circuit includingsaid holdingswitch andl said combustion switch contacts, said second`v and third circuits being established byclosure of said holding switch, said combustionswi-tch contacts upon open-ing due to combustion establishment discontinuing said-third circuit, la four-th circuit established; bycombustion occurring and incl-udingmea-nstov close asecond heater switch, and' a iii-,thcircuit through said holding switch and includ-ing said heater; and a secondl heater switch, 'said second heaterswitchA being-- closed by energization of said last lmeans and; opened ley-energizat-ion of said -rst means-, saidheaterbeing-opera-bleupon energizationtoopensaidheater switch and being energized by closureof said combustion switch contacts as agresu-ltofcombusti-on` failure a-f-tercombustion; has once been established; said rstheaterswitch beingreclosedl after api-irgingperiod determined bythe back-to-.norrnal position.

1-0. I n anoilburner-system, a transformer -haytime required for said -rstheater switch to cool ins an intermediate tap for furnishing' two sourcesl of current supply, an initial room thcrmostat circuit connected across saidtransformer and including a room thermostat, an auxiliary heater switch, means operable uponenergization by closure ofA thel room'; thermostat' to4 initiate operation ofthe burner, aisafetyswitch heater, and combustionV switch contacts, in said-` initial room thermostat circuit, saidjcombustion switch contacts being closed in the absence Vand` cpen inv the presence. of combustiom a second'setV of combustion switch contactsopen, in the absence and closed, inthe presence of combustion. a

safety "switch normally closed; butopenedrby said safety switchheater upon predeterminedienergization thereof, a holding switch closedjby energizatmn. ofsaid means' and connected with said initial*room,thermostat` circuity iordiyidingl itso ythatupon closure-ofi the holding switchl a second circuit is established through said room ther- -mostat, said` auxiliary heater switch and said means, and a third circuit is established through said safety switch heater and said rst combustion switch contacts, said rst combustion switch contacts upon failure to open dueto failure of Vcombustion to be established effecting opening of said safety switcha fourth circuit including said second combustion switch contacts, an ignition trip coil and an ,ignition trip coil switch, an ignition switch for the burner closed by said vmeans when energized and opened by said ignition trip coil when it is energized, said ignition trip coil switch being also opened by said yignition trip coil to de-energze the trip coil subsequent to openingrof the ignition switch thereby, and a fifth circuit through said holding switch including an sure of said first combustion switch contacts by closure of the room thermostat to initiate op- Y eration of the burner, a safety switch heater, and combustion switch contacts in said initial room thermostat circuit, said combustion switch contacts beingclosed in the absence and open in the presence of combustion, a second set of combustion switch contacts open in the absence and closed in the presence of combustion, a safety switch normally closed but opened by said safety switch heater upon predetermined energization thereof, a holding switch closed by energization 'off said means' and connected with said initial room thermostat Vcircuit for dividing it so that upon closure ofthe holding switch a second circuitis established through said room thermostat,'said auxiliary heater switch and said means, f

anda third circuit is established through said safety switch heater and said first combustion switch contacts,` said second and third circuits being thereby established and said initial room thermostat being altered as to current supplied thereto, said first combustion switch contacts upon failure to open due to failure of combustion to be established effecting opening of said safety switch, a fourth circuit including said second combustion switch contacts, an ignition trip coil, an ignition switch for the burner closed by said means when energized and opened by said ignition trip coil when it is energized, and a fifth circuit through said holding switch including an auxiliary heater and a second auxiliary heater switch, said second auxiliary heater switch being closed by energization of said ignition trip coil and opened by energization of said means, said auxiliary heater being operable upon energization to open said auxiliary heater switch in a period of time shorter than the period of time required to open said safety switch upon energization of said safety switch heater, said auxiliary heater being energized by closure of said first combustion switch contacts as a result of com- Cil bustion failure after combustion establishment,

said auxiliary heater switch being reclosed after a Vpurging period'determined by the timerequired Vfor said auxiliary heater switch to cool back to normal position.

12. In anv oil burner system, a 4transformer having an intermediate tap for furnishing two sources of current supply, an initial room thermostat cir-cuit connected across said transformer and including a room thermostat, a heater switch, a relay coil operable upon energization of closure of the room thermostat to initiate operation of the burner, and combustion switch contacts ,in said initial room thermostat circuit, said combustion switch contacts being closed in the absence and open in the presence of combustion, a second set of combustion switch contacts open in the absence and closed in the presence of combustion, a holding switch closed by energization of said relay coil and connected with said initial room thermostat circuit for dividing it .so that upon closure of the holding switch a second circuit is established through said room thermostat, said auxiliary heater switch and Vsaid relay coil, and a third circuit is established'through said rst combustion switch contacts, a fourth circuit including said second combustion switch contacts and a trip coil, and a fifth circuit through said holding switch and including a heater and a second heater switch, said second heater switch being closed by energization of said trip coil and opened by energization of said relaycoil, said heater being operable upon energization t0 open said rst lheater switch, said heater being energized by closure of said first combustion switch contacts as a result of combustion failure after combustion establishment, said yrst heater switch being reclosed after a purging period determined by the time required for said heater switch to cool back to its cold position.

13. In a control system for oil burners, a transformer, a room thermostat, a relay operable upon energization to cause voperation of the burner, a circuit including the secondary of said transformer and said relay and controlled by said room thermostat, said room thermostat establishing said circuit upon closure of the room thermostat, means thereafter operable to main- ,tain said relay` energized from a portion only of saidk secondary, combustion switch contacts and a safety switch actuator in the other portion of said secondary circuit, said combustion `switch Acontacts being normallyv closed but opened upon the presence of combustion, a heater, a heater switch/in circuit with said room thermostat an'd' opened: by' vsaidV heater to open said means, to energize said heater and thereby effect opening of said heater switch and shutting off of the system by de-energization of said relay, the system subsequently recycling after a time period upon reclosure of said heater switch as a result of cooling thereof, the cooling of said l the burner, av .circuit including a safety switch Y heater for said safety switch and said relay and controlled by said room thermostat-saidv room thermostat establishing said circuit upon closure of the roomthermostat, meansV thereafter operable to, maintain'said relay energized through a holding circuit from said source of current supply,

VYcombustion'[switch contacts. and a safety switch actuator in Aanother circuit. fromlsaid VsourceV of current supply, said combustions/witch contacts being normally closed but. opened upon the presence of combustion, an 'auxiliary heater, an auxiliaryA heater yswitch .in `circuit vsaid room' thermostat and opened by said auxiliaryV heaterhto open said Yroom .thermostat circuit and thereby ie-energize said relay, .said auxiliary heater being controlled by said combustion switch contacts and havinga second auxiliary heater switch openedfby said relay, another-.holding circuit in .which vsaid-second auxiliary'heater switch is located',said last circuit including Vmeans ,responsiveto combustion establishment to effect closure of .said second' auxiliary heater .switch whereby Vu'pon combustion failure subsequentY to Ncombustion .establishment closure. of said combustion switch 4contacts will effect completion of said auxiliary heater circuit through said second auxiliary heaterr switch and said second means, tov energize said auxiliary heater and thereby effect opening of Vsaid auxiliary heater switch and shutting olf of the system 4by de-energization. of said relay, the system subsequently recyclingY after a, timeV 'periodi upon reclosure of said auxiliary heater switchas a result of cooling thereofY (said auxiliary heater 4effecting opening of` said auxiliary heater switch more quickly than opening of said safety switch as a result o'fxenergization of 'saidsafety switch heater and the cooling 'of saidauxiliary switch vrequiring-lsufiicient `time Vto providev aY .purging period for .the burner). 15. In a control systemv of the character de,-

V scribed, .a transformer,l a: room thermostat, a

an actuator .switch in circuit with'said room thermostat and opened. by said recycling actuatork to.Y open saidnro'om .thermostat circuit and thereby ,de-energize; said recycling relay, 'said actuator being. controlled by said Acombustion switch contacts and having a second actuator Lswitch opened bynsaidrelay, said means being also. in circuiti with said second actuator switch, means responsive .to combustion establishment to effect closure of said secondV actuator switch whereby upon combustion vfailure subsequent to combustion establishment closure of said combustion switch contacts will effectY completion of said actuator circuitA through said rst means, said second actuator switch and said second means, to energize said actuator and thereby effect opening of said actuator switch and shutting off of thesystem by de-energization of,V said relay, the 'system subsequently recycling after a' time period upon reclosure of said'recycling actuator switch as a result of cooling of said thermally operable' recycling actuator, the cooling of said recyling actuator requiring sufficientV Y time to provide a purgingyperiod.

16. In a burner control system, a. relay circuit l including a room thermostaaa recycling actuator switch and closed cold contacts of'a combustion switch,ra recycling actuator, said actuator switch being openedby energization thereof and closed after a time period Yof Ade-energization thereof, a second actuator switch in circuit with said actuator, said'second actuator switch being opened by said relay, 4and* means responsive to closed hot contacts of said combustion switch to .close said second actuator switch whereby, upon ,combustion failure following combustion establishment and resulting closure of said closed cold contacts of said combustion switch,lsaid actuator Vwill be energized and effect a purging period of non-operation of said burner followed by a recycling of the system.`v r j i 17. In an oil burner control system, a relay circuit including a room thermostat, an auxiliary relay operable upon `energization to causev oper- Y ationY of .a burner 'or the like, a circuit including the secondary of said transformer and said. relay and controlled by 'said room thermostat, said room thermostat lestablishing said circuit upon closure of the room. thermostat, means thereafter operable to ,maintain said relay energized from a portion only of said'secondary, vcombustion switch contacts and a safety switch actuator in the other portion of said secondary circuit,

said combustion switch contactsbeingA normally closed butopened upon the .presence of combustion, athermally operable recycling actuator,

heater switch, a safety switch heater and closed cold, contacts of a combustion switch, an auxiliary heater, anauxiliary heater switch opened e by energization thereofand closed after artime period by de-energization thereof, a second auxilliary heater switch in circuitwith said -auxiliary heater, said ,second auxiliary Vheater switch being opened bysaidjrelay, vmeans responsive to closed hot, contacts of -said combustion switch to close said second |auxiliary heater switch whereby, upon combustionr failure fol-lowing combustion .establishment and resultingvclosure of said closed cold'contacts vof, said combustion switch, said auxiliary heater will be energized and effect a purging period of non-operationof said burner followed by Ya recycling of the system, and a. safety switch controlled by Ysaid safety switch heater and operable to shut down the system in Vthe eventrcombustion fails to be established.

i, BURTON E. SHAW'. 

